Image display apparatus

ABSTRACT

A cabinet accommodates therein a discharge lamp  13,  an ignitor module  7  applying a high voltage to the discharge lamp  13  for igniting the same, a lighting device  8 A which is connected to the ignitor module and applies a discharging voltage to the discharge lamp so as to keep the discharge lamp turned on, a signal processing unit  9  providing an image signal in accordance with an input signal, an image display which, in response to the image signal from the signal processing unit, produces an image to be projected by use of a light of the discharge lamp  13,  and a power supply supplying electric power to the above parts. At least a high voltage generating unit of the ignitor module  7  is arranged to be separated from the lighting device  8 A and is disposed away from the signal processing unit  9  and close to the discharge lamp  13  for restraining malfunction of the signal processing unit.

TECHNICAL FIELD

The present invention is related to an image display apparatus forenlarging and projecting an image and picture on an image displayingelement such as a liquid crystal projector, DLP projector, and a rearprojection TV.

BACKGROUND ART

Referring to FIGS. 14 to 14, an explanation is made for a projector asone example of the image display apparatus such as a liquid crystalprojector, DLP projector, and rear projector for enlarging andprojecting still images and moving images from a personal computer, aswell as video image or TV pictures from a video camera or videorecorder.

FIG. 14 is a perspective view illustrating an arrangement of parts of aprior projector without a cabinet (but indicated by dotted lines). FIG.15 is a top view illustrating the part arrangement within the projectorof FIG. 14. FIG. 16 illustrates a structure of a lamp house fittedwithin the same projector. FIG. 17 is a circuit block diagram of thesame projector.

The image display apparatus (projector) 1PA includes a cabinet 2, animage display 3, the lamp house 4, a projection lens 5, a power supply6, an ignitor module 7, a lighting device 8, a signal processing unit 9,a plurality of forced-air cooling fans 10, and an input filter 11.

The cabinet 2 forms a case which covers the whole projector, and isprovided with the signal processing unit 9 extending on back and top ofthe cabinet 2 except for the lamp house 4.

The image display apparatus 1PA is connected to an AC mains 26 throughan AC input cable 16. The AC input cable 16 is connected to the powersupply 6 through the input filter 11. The voltage of the AC mains is,for example, 100 to 240 AC Volts, which is converted at the power supply6 into DC voltages, such as DC 370 V, DC 12 V, DC 5 V, DC 3.3 V.

Connected to the power supply 6 are the signal processing unit 9 and thelighting device 8. The image display 3 is connected to the signalprocessing unit 9. The image display 3 includes an image displayingelement 3 a formed as a liquid crystal display or DMD element, and anoptical system composed of a condenser lens and a prism (not shown) forfocus control of a light from the discharge lamp 13. The imagedisplaying element 3 a receives an image signal output from the signalprocessing unit 9 to give the resulting image which is projected bymeans of a light from the discharge lamp 13 of which focus is controlledby the above optical system.

The lighting device 8 is connected to the lamp house 4. In detail, thelamp house 4 includes a high intensity discharge lamp 13, a reflector13, and a lamp socket 14 b (see FIG. 16). The discharge lamp 13 such asa metal halide discharge lamp and super high pressure mercury dischargelamp (refer to Japanese Patent Publication Nos. 2-138561 and 6-52830 forexample) is connected to the lighting device 8 through high voltage leadwires 12 and the lamp socket 14 b. The lamp house 4, which is detachableto the projector so that the user or operator can replace the dischargelamp 13, is partly or entirely made of a resin. Numeral 42 in FIG. 16indicates a fixture of the reflector 30.

The projection lens 5 receives the light from the discharge lamp 13through the image display 3 in order to enlarge and project the image orpicture given to the image display 3.

The power supply 6 includes a rectifier 6 a, a controller 6 b, aboosting chopper circuit 6 c, and four DC output circuits 6 d to 6 g.The rectifier 6 a converts the input AC voltage into the DC voltage. Thecontroller 6 b controls the boosting chopper circuit 6 c. The boostingchopper circuit 6 c includes an inductance L1, a MOSFET (Q1), a diodeD1, and a smoothing capacitor C1 to output a DC voltage boosted to adesired level by switching the MOSFET (Q1). The DC output circuits 6 dto 6 g are respectively DC-DC converters which convert the output of theboosting chopper circuit 6 c into desired DC voltages for supplying thesame to the corresponding units. The DC output circuits 6 d to 6 fsupply appropriate DC voltages to the signal processing unit 9, whilethe DC output circuit 6 g supplies an appropriate DC voltage to thelighting device 8.

The lighting device 8 includes a controller 8 a, a step-down chopper 8b, a polarity inverting circuit 8 c, resistors R2, R3 for lamp voltagedetection, and a resistor R4 for lamp current detection. The controller8 a is supplied with a DC output from the DC output circuit 6 g througha capacitor C7 so as to control the step-down chopper 8 b and thepolarity inverting circuit 8 c based upon the lamp voltage and the lampcurrent respectively monitored by lamp voltage detection resistors R2,R3 and the lamp current detection resistor R4. The step-down chopper 8 bincludes a MOSFET (Q2), a diode D2, an inductance L3, and a capacitor C3to step-down the input DC voltage supplied through a noise filtercomposed of an inductance L2 and a smoothing capacitor C2 for stablyproviding the electric power necessary to the discharge lamp 13 byswitching the MOSFET (Q2). The polarity inverting circuit 8 c, composedof MOSFETs (Q3 to Q6), inverts the polarity of the DC output of thestep-down chopper 8 c by switching MOSFETs (Q3, Q6) alternately withMOSFETs (Q4, Q5), thereby providing an AC power to the discharge lamp13.

The ignitor module 7 includes a resistor R1, capacitors C4 to C6, asidac SSS, transistors T1, T2, a diode D3, and a spark-gap (GAP). Theignitor module 7 derives its operating voltage from the output voltageof the step-down chopper circuit 8 b within the lighting device 8 so asto apply high voltage pulses (for example, 18 kVo-p) between electrodesof the discharge lamp 13, bringing about a breakdown to thereby startlighting the lamp.

The signal processing unit 9 is connected at its input end to thepersonal computer, video recorder or the like through a signal cable 17,and at its output end to the image displaying element 3 a of the imagedisplay 3. The signal processing unit 9 receives an RGB signal or TVsignal from the computer, video recorders or the like connected to thesignal cable 17, and outputs a signal for displaying the image on theimage displaying element 3 a.

The forced-air cooling fans 10 are provided for avoiding a temperaturerise of the heat-generating parts within the image display apparatus 1,and disposed respectively adjacent to the ignitor module 7, the powersupply 6, and the lamp house 4.

The operation of the ignitor module 7 will be now explained in detail.

The ignitor module 7 operates on the output voltage from the step-downchopper circuit 8 b, which charges capacitor C4 through resistor R1 sothat sidac SSS become conductive to release the electric chargesaccumulated in capacitor C4 when capacitor C4 is charged to a break-overvoltage of sidac SSS.

At this occurrence, a transient voltage is caused by a transientphenomenon in combination with an inductance as viewed from the primaryside of the transformer T1, and is transferred to the secondary side oftransformer T1, followed by being rectified to accumulate charge incapacitor C5. This action is repeated to increase the charged voltageacross capacitor C5. When capacitor C5 is charged to the break-overvoltage of the spark-gap (GAP), the spark-gap (GAP) conducts todischarge the capacitor C5. Upon this discharging, a voltage developedby a transient phenomenon in combination with an inductance as viewedfrom the primary side of transformer T2, is boosted at transformer T2and is then output as high voltage pulses.

A recent technical problem for the projector concerns with alight-and-compact design for portability.

In making the projector compact, it is noted that the ignitor module 7for igniting the light source of the discharge lamp 13 generates highvoltage pulses which, as shown in FIG. 18, include frequency componentsof several MHz, and is cause to leak from the high voltage lead wires 12by way of “floating capacitance” present in various portions of thecabinet 2 while the pulses are fed through a transmission path(including the high voltage lead wires 12) from the ignitor module 7 asthe high voltage pulse source to the discharge lamp 13. Thus leakedportion of the high voltage is voltage-divided by the floatingcapacitance to be dispersed to various portions of the cabinet 2.

Although the high voltage pulses are damped, they will be transmitted tomicrocomputer or IC in the signal processing unit 9 within the cabinet 2due to this floating capacitance. When the high voltage pulses finallyreaching the microcomputer or IC still have a voltage higher than asurge (or electrostatic) withstand at the corresponding terminals of themicrocomputer or IC, the microcomputer or IC of the signal processingunit 9 will malfunction or even the signal processing unit 9 will bebroken at the worst. In order to make a protection against thisoccurrence, the high voltage lead wires 12 should be made as short aspossible and at the same time as thick as possible.

While, on the other hand, because of that the ignitor module 7 derivesits operating voltage from the output voltage of the lighting device 8and also because of that both of the ignitor module 7 and the lightingdevice 8 have their outputs connected to the discharge lamp 13, theignitor module 7 and the lighting device 8 are formed commonly on asingle board such that the ignitor module 7 and the lighting device 8thus integrated together are disposed away from the signal processingunit 9 and close to the discharge lamp 13. Since the power supply 6 isdisposed remote from the ignitor module 7 and the lighting device 8 forthe discharge lamp 13, the ignitor module 7 and the lighting device 8are provided with the noise filter 15 composed of inductance L1 andcapacitor C2 in order to receive the electric power from the powersupply 6.

Since the lighting device 8 is made active to keep the discharge lamp 13turned on and is disposed adjacent to the discharge lamp 13, it issubject to a heat radiation from the discharge lamp 13 such that theelectronic parts of the lighting device 8 suffer from increasedtemperature rise also in combination with heat resulting from a powerloss of the lighting device 8 itself. In order to avoid this occurrence,it is necessary to provide the forced-air cooling fan 10 for thelighting device 8 or to design the path of the forced-air cooling flowwithin the cabinet 2.

Taken the above points into consideration, the projector of FIGS. 14 to17 is designed.

Japanese Patent Publication No. 7-114805 discloses a lighting apparatusfor vehicle's head lamp, which is different from the image displayapparatus of the present invention. The lighting apparatus includes alamp body integrating a reflector, a discharge lamp integrated withinthe lamp body together with the reflector, a ballast for stably lightingthe discharge lamp, and an ignitor applying a high starting voltage tothe discharge lamp at the starring thereof. The ignitor has a highvoltage generating unit which receives a low voltage input to generate ahigh voltage, and which is formed integrally with a connecting unit forthe discharge lamp. The ballast and the ignitor is connected to the lampbody in such a manner that at least the connecting unit of the highvoltage generating unit of the ignitor is exposed to the interior of thelamp body. In this lighting apparatus for the vehicle's headlamp, amounting unit for mounting the discharge lamp is not formed as integralpart of the high voltage generating unit.

U.S. Pat. No. 3,180,981 proposes a technique in which a lighting devicefor an air-cooled projection lamp has high frequency terminals and isaccommodated within a lamp house provided with an exhaust port in itstop. The lighting device has its output connected to the lamp throughhigh voltage lead wires and not at the high frequency terminals. Anintake port for the lamp cooling air flow and the exhaust port are notlimited to particular surfaces of the lamp house. Also, the interior ofthe image display apparatus and the lamp house are configured such thatthe air-cooling flow path is established when a cabinet of the imagedisplay apparatus is fitted with the lamp house.

U.S. Pat. No. 4,902,943 discloses a plug-in starting aid apparatus whichis connected to a ballast as a starting circuit of a high intensitydischarge lamp for providing high voltage pulses. In this apparatus, atleast three terminals project from one face of a frame, the first onebeing connected a voltage-responsive switch, the second one beingconnected to a capacitor, and the third one connected to the end of adischarging loop. In this connection, the present invention as describedlater is not limited to the disclosed feature that the I/O terminalsproject out of a casing as well as that the individual terminals areprovided for connection to the voltage-responsive switch, the capacitorand the end of the discharging loop, respectively.

However, the prior art structure has technical problems that theadditional parts (noise filter 15, forced-air cooling fans 10 and thelike) around the lighting device are required and that the signalprocessing unit 9 suffers from a malfunction due to that fact that thesignal processing unit 9 are arranged within a narrow space togetherwith the ignitor module 7 generating the high voltage pulses as well asthe high voltage lead wires. Accordingly, it has been desired torestrain the malfunction of the signal processing unit 9, and morepreferably, to prohibit the failure, to make the apparatus compact, toreduce the operational noise, to delimit the influence of the noise tothe electronic circuitry, and to increase design flexibility.

Dilsclosure of the Invention

The present invention has been accomplished in view of the aboveproblems and has an object of providing an image display apparatus whichis capable of restraining the malfunction of the signal processing unit.

The image display apparatus according to the present invention includesa cabinet which accommodates therein a discharge lamp, an ignitor modulewhich applies a high voltage to the discharge lamp for igniting thesame, a lighting device which is connected to the ignitor module andapplies a discharging voltage to the discharge lamp so as to keep thedischarge lamp turned on, a signal processing unit providing an imagesignal in accordance with an input signal, an image display which, inresponse to the image signal from the signal processing unit, producesan image to be projected by use of a light of the discharge lamp, and apower supply supplying an electric power to the ignitor module, thelighting device, the signal processing unit, and the image display. Inthis arrangement, at least a high voltage generating portion of theignitor module is arranged to be separated from the lighting device andis disposed away from the signal processing unit and close to thedischarge lamp, thereby restraining the malfunction of the signalprocessing unit. Also, since the high voltage generating portion of theignitor module can itself form a single block so as to be freelyarranged, in contrast to the prior art ignitor module which isincorporated into the lighting device, it can be arranged closed to thedischarge lamp to reduce the leakage of the high voltage being appliedto the discharge lamp, thereby enabling to reduce the malfunction orfailure of the signal processing unit composed of electronic componentssuch as a microcomputer and IC. Further, since the lighting device isaway from at least the high voltage generating portion of the ignitormodule, it can be arranged in a position not exposed to heat from thedischarge lamp, whereby it is possible to reduce heat stress applied tothe lighting device, and even to reduce the number of the forced-aircooling fans by suitably arranging the lighting device.

The ignitor module is preferred to have a lamp socket for restrainingthe high voltage pulsed from leaking to other portions by way offloating capacitance, thereby further restraining the malfunction orfailure of the electronic circuitry of the microcomputer or IC.

Further, when the lighting device and the power supply are mounted on acommon board, it is possible to eliminate the noise filter forsuppression of high frequency noise superimposed on a connection linebetween the lighting device and the power supply and also to eliminateconnectors for connection therebetween.

When the ignitor module is connected to the lighting device by wires, itis also possible to restrain the malfunction of the signal processingunit.

When the ignitor module and the lighting device are mounted on aflexible printed board, it is possible to eliminate the wires and togive an arrangement in which the ignitor module can be physicallyseparated from the lighting device.

When the signal processing unit, the power supply, and the lightingdevice are mounted on opposite side of the ignitor module from thedischarge lamp, it is possible to restrain the high voltage pulses fromleaking to the other portions by way of the floating capacitances forrestraining the malfunction or failure of the electronic circuitry ofthe microcomputer or IC.

Preferably, the ignitor module is composed of a high voltage generatingcircuit which applies the high voltage to the discharge lamp, and apower source circuit which is connected to the lighting device andprovides an electric power to the high voltage generating circuit. Also,a lamp house is provided to be the cabinet and to have its interiorspace separated by a partition into two storage spaces, one forreceiving the discharge lamp, and the other for receiving the highvoltage generating circuit. Thus, the partition separating the twostorage spaces can interrupt the heat radiation and ultravioletradiation of the discharge lamp from reaching directly to the highvoltage generating circuit of the ignitor module, avoiding thedeterioration of the high voltage generating circuit of the ignitormodule as well as the lowering of long-term reliability. As the lamphouse is detachable to the cabinet, the high voltage generating circuitcan be replaced with a new one simultaneously at the time of replacingthe discharge lamp reaching its lamp life end, thereby realizing toprovide a projector which is highly reliable in the ignition performanceover a long-term use.

The high voltage generating circuit is surrounded by a case havingwalls, at least one of the walls forming an outer wall of the lamphouse. With this arrangement, the case can interrupt the heat radiationand ultraviolet radiation of the discharge lamp from reaching directlyto the high voltage generating circuit of the ignitor module, avoidingthe deterioration of the high voltage generating circuit of the ignitormodule as well as the lowering of long-term reliability.

The above partition is preferred to interrupt the heat radiation fromthe discharge lamp to the high voltage generating circuit.

Within the lamp house, there are provided lead wires for connection ofthe high voltage generating circuit to the power circuit of the ignitormodule, and for connection of the discharge lamp to the lighting device,respectively. Preferably, the lamp house is provided with a partitionwhich is disposed between the lead wires and the discharge lamp.Whereby, the partition can interrupt the heat radiation and ultravioletradiation of the discharge lamp from reaching directly to the leadwires, avoiding the deterioration of the lead wires as well as thelowering of long-term reliability.

Preferably, the cabinet includes a fan which makes a forced-air coolingfor the interior of the cabinet, and the high voltage generating circuitis arranged upstream of the discharge lamp with respect to a forced-airflow of the fan. With this result, the high voltage generating circuitof the ignitor module can efficiently radiate the heat.

Preferably, the high voltage generating circuit is connected to thedischarge lamp through high voltage lead wires which extend from thehigh voltage generating circuit on its side adjacent to the dischargelamp. Thus, at the time of igniting the discharge lamp, it is possibleto restrain the high voltage pulse generated at the high voltagegenerating circuit of the ignitor module from leaking through thefloating capacitances present around various portions of the cabinet,reducing the danger of malfunctioning or breaking the microcomputer orIC.

The ignitor module is preferred to be separated into a high voltagegenerating unit for applying the high voltage to the discharge lamp anda power source unit which supplies an electric power to the high voltagegenerating unit. Thus, it is possible to restrain the malfunction orfailure of the signal processing unit, to make the apparatus compact andlight-weight, to reduce the operational noise, to delimit the influenceof the noise to the electronic circuitry, to increase designflexibility, and yet to improve reliability of the apparatus even whenthe lamp house could not afford the space for accommodating the entireignitor module.

The high voltage generating unit may be arranged close to the dischargelamp, enabling to improve reliability of the apparatus even when thelamp house could not afford the space for accommodating the entireignitor module.

Preferably, the high voltage generating unit is arranged closer to thedischarge lamp than the power source unit, thereby enabling to restrainthe malfunction or failure of the signal processing unit, to make theapparatus compact and light-weight, to reduce the operational noise, todelimit the influence of the noise to the electronic circuitry, toincrease design flexibility.

At least the high voltage generating unit is preferred to be arranged inthe lamp house detachably receiving the discharge lamp. Thus, it is easyto modify the design of the high voltage generating unit of the ignitormodule.

The lamp house is preferred to include a storage section receiving atleast the high voltage generating unit for effectively avoiding themalfunction of the signal processing unit.

Preferably, the storage section is filled with an insulation material toenhance the insulation of the high voltage generating unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit block diagram of an image display apparatus inaccordance with a first embodiment of the present invention.

FIG. 2 illustrates the internal structure of the image displayapparatus.

FIG. 3A is a perspective view of the ignitor module separated from acombined assembly of an image display apparatus in accordance with asecond embodiment of the present invention, FIG. 3B illustrates the faceas viewed from B in FIG. 3A, and FIG. 3C illustrates the face as viewedfrom A in FIG. 3A.

FIG. 4 is a perspective view illustrating an arrangement of variousparts of an image display apparatus in accordance with a fifthembodiment of the present invention.

FIG. 5 is a view illustrating the arrangement of various parts of theabove image display apparatus.

FIGS. 6A, 6B, and 6C are respectively top view, rear view, and side viewof a lamp house of the above image display apparatus.

FIG. 7 is a circuit block diagram of the above image display apparatus.

FIG. 8 is an explanatory view for the air-cooling within the lamp houseof the above image display apparatus.

FIG. 9 is a circuit diagram of an image display apparatus in accordancewith a sixth embodiment of the present invention.

FIG. 10 is a partial circuit diagram of the ignitor module of FIG. 9.

FIGS. 11A, 11B, and 11C are respectively top view, rear view, and sideview of a lamp house of the above image display apparatus of FIG. 9.

FIG. 12 is a circuit diagram of an image display apparatus in accordancewith a seventh embodiment of the present invention.

FIG. 13 is a partial circuit diagram of the ignitor module of FIG. 12.

FIG. 14 is a perspective view illustrating the arrangement of variousparts within a prior projector shown with a cabinet being removed.

FIG. 15 is a top view illustrating the arrangement of the various partswithin the projector.

FIG. 16 illustrates the structure of a lamp house fitted within theabove projector.

FIG. 17 is a circuit block diagram of the above projector.

FIG. 18 is a waveform chart of high voltage pulses generated at theignitor module.

BEST MODES FOR CARRYING OUT THE INVENTION

<First Embodiment>

FIG. 1 illustrates a circuit block diagram of an image display apparatusin accordance with a first embodiment of the present invention. FIG. 2illustrates the internal arrangement of the above image displayapparatus.

The image display apparatus 1 is arranged differently from the prior artin that the power supply 6 and the lighting device 8A are mounted on acommon board as a combined assembly 6A but excluding the noise filter15, capacitor C7, and the ignitor module 7, and in that the lightingdevice 8A of the combined assembly 6A is connected to the separateignitor module 7 by means of wires bridging between output terminals(a1-a2) and (b1-b2), and in that the high voltage lead wires 12 are madeshort. The other arrangements are identical to those explained and thelike parts are designated by the like numerals without duplicateexplanation thereof.

As a consequence of that the ignitor module 7 is connected to theseparately formed lighting device 8A, the polarity inverting circuit 8 cof the lighting device 8A is connected to the ignitor module 7 by meansof wires between output terminals (c1-c2) and (d1-d2).

According to the first embodiment, the high voltage lead wires 12connecting the ignitor module 7 and the discharge lamp 13 are made shortso that the high voltage pulses generated at the ignitor module 7 areapplied to the discharge lamp 13 only through a minimum path, therebyrestraining the high voltage from leaking through floating capacitanceto other portions and therefore restraining the malfunction or failureof the electronic circuit of the microcomputer or IC. Also, it ispossible to restrain the attendant noise from spreading to theelectronic circuit board (except for the lighting device 8A) forprocessing image signals within an electromagnetically shielded space.

Further, since the power supply 6 and the lighting device 8A are mountedon the common board, it is possible to increase a removable space 20(see FIG. 2), to eliminate one of the force-air cooling fans 10, andalso to eliminate the noise filter 15 and the connector that arenecessary for connection of the power supply 6 and the lighting device 8as shown in FIG. 17, thereby realizing the compact and light-weightarrangement of the image display apparatus 1. Further, by theelimination of the force-air cooling fan 10, it is possible to reducethe noise level and therefore the operational noise of the image displayapparatus 1.

It is noted that the ignitor module 7 for the projector is designed forlarge current and high voltage and is a most bulky part among the partsforming the lighting device of FIG. 17. However, by separating theignitor module 7 from the lighting device 8A, it is possible to improvedesign flexibility of the image display apparatus 1.

As seen in FIG. 2, the ignitor module 7 is disposed on one side (lowerleft side in the figure) of the discharge lamp 13, while the signalprocessing unit 9 and the combined assembly 6A are disposed on the otherside (upper and right sides in the figure). Thus, the high voltagepulses can be restrained from leaking to the other side through thefloating capacitance, thereby restraining the malfunction or failure ofthe electronic circuitry of the microcomputer or IC.

<Second Embodiment>

FIG. 3A is a perspective view illustrating the ignitor module shown asbeing detached from the combined assembly 6A with regard to the imagedisplay apparatus in accordance with the second embodiment of theinvention, FIG. 3B is a B-direction face view for illustration ofconnecting terminals (a2, b2, c2, and d2) for connection with thecombined assembly 6A, and FIG. 3C is a C-direction face view forillustration of a lamp socket 14 a fixed to the ignitor module 7.

The image display apparatus of the second embodiment differs from thefirst embodiment in that the ignitor module 7 is provided with the lampsocket 14 a. The other structures are identical to the first embodimentand are referenced by the same numerals without the duplicateexplanation thereof.

According to the second embodiment in which the ignitor module 7includes the lamp socket 14 a, it is possible to restrain the highvoltage pulses from leaking to the other portions through the floatingcapacitance and therefore restrain the malfunction or failure of theelectronic circuit of the microcomputer or IC.

<Third Embodiment>

The image display apparatus in accordance with the third embodiment ofthe invention differs from the first embodiment in that the ignitormodule 7 is connected to the lighting device 8A by means of wires.

According to the third embodiment, the ignitor module 7 is connectedthrough the wires to the lighting device in the combined assembly 6A togive a physical distance between them in order to obtain the same effectas in the first embodiment.

<Fourth Embodiment>

The image display apparatus in accordance with the fourth embodiment ofthe invention differs from the first embodiment in that the ignitormodule 7 and the combined assembly 6A have their circuits formed on aflexible printed board.

According to the fourth embodiment in which the ignitor module 7 and thecombined assembly 6A have their circuits formed on the flexible printedboard, it is made to give a physical distance between the ignitor module7 and the lighting device 8A of the combined assembly 6A for realizingthe same effect as the first embodiment.

<Fifth Embodiment>

FIG. 4 is a perspective view illustrating various parts within the imagedisplay apparatus in accordance with the fifth embodiment of theinvention. FIG. 5 is a top view illustrating the various parts of theimage display apparatus. FIGS. 6A, 6B, and 6C are respectively top view,rear view, and side view of the lamp house of the image displayapparatus. FIG. 7 is a circuit block diagram of the image displayapparatus. The like parts and structures are indicated by the likereference marks and duplication explanation thereof is omitted.

According to the fifth embodiment, the ignitor module 7 shown in FIG. 1is divided into a power source circuit 7 a composed of resistor R1,capacitor C1, and sidac SSS, and a high voltage generating circuit 7 bcomposed of transformers T1, T2, diode D3, capacitors C5, C6, andspark-gap (GAP).

The power source circuit 7 a is arranged within the lighting device 8Aof the combined assembly 6A mounted/on the board. Hereinafter, thelighting device BA additionally incorporating the power source circuit 7a is referred to as lighting device 8B, whereas the combined assembly 6Ais referred to as the combined assembly 6B. Further, the high voltagegenerating circuit 7 b is arranged within the lamp house 4. Hereinafter,the lamp house 4 accommodating therein the high voltage generatingcircuit 7 b is referred to as the lamp house 4A.

The lamp house 4A is made detachable to the cabinet 2, and is formedpartly or entirely by a plastic resin. The discharge lamp 13 is disposedwithin the lamp house 4A with its optical axis aligned in thelongitudinal direction of the lamp house. A reflector 30 is disposed toextend from behind the lamp to the forwardly of the lamp. The lamp houseis formed on either opposite side with an outer shell 31 and has itsrear opened. The outer shell 31 at one side of the lamp house is formedwith a partition 32 which extends from the rear of the outer shell intointerior of the lamp house 4A to give a lamp storage space 38 foraccommodating the discharge lamp 14 and an ignitor storage space 33 foraccommodating the high voltage generating circuit 7, which spaces areseparated from each other by the partition 32.

The high voltage generating circuit 7 b received within the ignitorstorage space 33 is surrounded by a case 39 which is provided on itsfront end with a bushing 34 for drawing out the two high voltage leadwires 12, and on its rear end with the four lead wires 36 for supplyingthe input power to the high voltage generating circuit 7 b. The oppositeside walls of the case 39 share the outer walls of the lamp house 4A.The partition 32 separating the lamp storage space 38 from the ignitorstorage space 33 is cooperative with the casing 39 to interrupt the heatradiation and ultraviolet radiation from the discharge lamp 13, enablingto avoid the deterioration as well as the lowering of the long-termreliability of the high voltage generating circuit 7 b.

The high voltage lead wires 12 are drawn out from the front end of thehigh voltage generating circuit 7 b, i.e., from a portion adjacent tothe input terminals of the discharge lamp 13 so as to connect the highvoltage generating circuit 7 b to the discharge lamp 13 by a minimumdistance. Whereby the high voltage pulses generated from the highvoltage generating circuit 7 b at the time of starting the lamp can berestrained from leaking through floating capacitances present at variousportions of the cabinet 2, reducing the danger of the malfunction orfailure of the microcomputer or IC.

The lead wires 36 are provided for connection of the lighting device 8Bto a lamp socket 25 b on the rear at one side of the lamp house 4A. Thelamp socket 25 b is coupled to an associated lamp socket 25 a at theoutput end of the lighting device 8B (terminals a3, b1, c1, d1 of 25 acorresponds to terminals a4, b2, c2, and d2 of 25 b), so that the outputfrom the lighting device 8E is supplied to the high voltage generatingcircuit 7 b as well as to the discharge lamp 13. The lamp socket 25 b isarranged in a spaced separated from the lamp storage space 38 by anL-shaped partition 37 formed on the rear end of the lamp storage space38 and is protected by the partition 37 which interrupts the headradiation and the ultraviolet radiation from the discharge lamp 13 foravoiding the deterioration and the lowering of the long-termreliability.

The power supply 6 and the lighting device 8B are mounted on the commonboard to thereby eliminate the noise filter 15 and the capacitor C7 asutilized in the prior art of FIG. 17.

Further, since the high voltage generating circuit 7 b is arranged closeto the discharge lamp 13, it is preferred to provide the force-aircooling fan 10 such that, as shown in FIG. 8, the flow direction Aextends from behind the lamp house 4A towards its front end. Thus, thehigh voltage generating circuit 7 b is disposed upstream of thedischarge lamp 13 with the air flowing along a direction of B, wherebyit is possible to reduce the amount of the radiant heat directing to thedischarge lamp as well as to radiate the heat of the high voltagegenerating circuit 7 b effectively.

It is noted that the spark-gap has its life-time which in turndetermines the life-time of the high voltage generating circuit 7 b andeven the projector. In the fifth embodiment, however, the high voltagegenerating circuit 7 b can be replaced with the new one at the time ofreplacing the discharge lamp 13, enabling to provide the projector whichis reliable over the long-term use in starting the lamp.

<Sixth Embodiment>

FIG. 9 is a circuit diagram of the image display apparatus in accordancewith the sixth embodiment of the present invention. FIG. 10 is a partialcircuit diagram of the ignitor module shown in FIG. 9. FIG. 11illustrates the manner in which the ignitor module of FIG. 10 isaccommodated. FIG. 1A is a top view, FIG. 11B is a rear view, and FIG.11C is a side view.

The image display apparatus in accordance with the sixth embodimentdiffers from that of the fifth embodiment in that, as shown in FIG. 9,the ignitor module includes the power source circuit 7 a formed as afront end between the step-down chopper circuit 8 b and the polarityinverting circuit 8 c of the lighting device 8B in the combined assembly6B, in addition to the high voltage generating circuit 7 c formed as arear end and separately from the power source circuit 7 a.

As in the fifth embodiment, the power source circuit 7 a is composed ofresistor R1, capacitor C4, sidac SSS arranged at the output of thestep-down chopper 8 b, and lamp socket 25 a. The lamp socket 25 aincludes a terminal (a3) connected one end of the sidac SS of whichother end is connected to a point between resistor R1 and capacitor C4,a terminal (b1) connected to the ground, a terminal (c1) connected to apoint between MOSFETs (Q3 and Q4), and a terminal (d1) connected to apoint between MOSFETs (Q5 and Q6).

The high voltage generating circuit 7 c is composed of the lamp socket25 b and the ignitor's major portion 70 connected to the lamp socket.The lamp socket 25 b has terminals (a4, b2, c2, and d2) connectedrespectively to the terminals (a3, b1, c1, and d1) of the lamp socket 25a. As shown in FIG. 10, the ignitor's major portion 70 is composed of ahigh voltage generating unit 72 generating the high voltage pulses, anda power source unit 71 at the rear end. The high voltage generating unit72 includes capacitors C5, C6, and a transformer T2 to generate the highvoltage pulses, while the power source unit 71 includes a transformerT1, a diode D3, and a spark-gap (GAP) to supply the electric power tothe high voltage generating unit 72 for causing it to generate the highvoltage pulses. As shown in FIG. 9, the ignitor's major portion 70 isconnected to the discharge lamp 13 through the high voltage wires 12(refer to FIG. 17), while the high voltage generating unit 72 isinterposed between the polarity inverting circuit 8 c and the dischargelamp 13.

Also in the sixth embodiment, the high voltage generating circuit 7 c isaccommodated within the lamp house 4B, as shown in FIG. 11. The highvoltage generating unit 72 is packed within the case 39, while the powersource unit 71 is disposed at a position remote from the high voltagegenerating unit 72. The power source unit 71 and the high voltagegenerating unit 72 are connected to each other by means of four leadwires 36. The case 39 is filled with a high dielectric resin (such asepoxy resin). Numeral 35 in FIG. A indicate the bushing. The four leadwires 36 may be equipped with intermediate couplers.

In the sixth embodiment thus configured, since the ignitor module isdivided into the power source circuit 7 a as the front end and the highvoltage generating circuit 7 c as the rear end, and also since the highvoltage generating circuit 7 c is further divided into the power sourceunit 71 and the high voltage generating unit 72, the high voltagegenerating unit 72 can be at least arranged within the lamp house 4B orin proximity thereto (within the lamp house 4B in FIG. 11) with theremaining parts arranged in the other space. Thus, even if the lamphouse 4B affords no space for accommodating the entire ignitor module,the ignitor module can be successfully assembled with increasedreliability.

Also, by changing the capacitance of capacitor C5 and the coil of thetransformer T2, it is possible to modify the characteristic of the highvoltage pulses as well as a tolerable limit for the load current (lampcurrent) flowing through the transformer T2, thereby changing only thehigh voltage generating unit 72 of the ignitor module in compliance withthe discharge lamps of different specifications. With this result, it ispossible to reduce the developing time, the investment to the formingdies, and the developing cost, thereby contributing to cut the wholecost and enabling to provide the ignitor module at the low cost and inshort-time period.

<Seventh Embodiment>

FIG. 12 is a circuit diagram of the image display apparatus inaccordance with the seventh embodiment of the present invention. FIG. 13is a partial circuit diagram of the ignitor module shown in FIG. 12.

The image display apparatus according to the seventh embodiment differsfrom that of the sixth embodiment in that, as shown in FIG. 12, theignitor module is composed of the power source circuit 7 d formed as afront end between the step-down chopper circuit 8 b and the polarityinverting circuit 8 c, and of the high voltage generating circuit 7 eformed as a rear end and separately from the power source circuit 7 d.

The power source circuit 7 d is composed of resistor R1, capacitor C4,sidac SSS arranged at the output of the step-down chopper 8 b, and lampsocket 27 a. The lamp socket 27 a includes a terminal (a3) connected oneend of the sidac SSS, a terminal (c1) connected to a point betweenMOSFETs (Q3 and Q4), and a terminal (d1) connected to a point betweenMOSFETs (Q5 and Q6).

The high voltage generating circuit 7 e includes a lamp socket 27 b andthe ignitor's major portion 70 a connected to the lamp socket 27 b. Thelamp socket 27 b has terminals (a4, c2, and d2) connected respectivelyto the terminals (a3, c1, and d1) of the lamp socket 27 a. As shown inFIG. 13, the ignitor's major portion 70 a includes the high voltagegenerating unit 72 e and the power source unit 71 a. The high voltagegenerating unit 72 e is composed of capacitors C5, C6, spark-gap (GAP),and transformer T2 to generating the high voltage pulses, while thepower source unit 71 a is composed of transformer T1 and diode D3 tosupply the electric power to the high voltage generating unit 71 a forcausing it to generate the high voltage pulses.

Also in the seventh embodiment, the high voltage generating circuit 7 eis accommodated within the lamp house 4D of the same configuration asthe lamp house of the sixth embodiment. The high voltage generating unit72 a is packed within the case 39, while the power source unit 71 a isdisposed at a position remote from the high voltage generating unit 72 a(refer to FIG. 11). The three lead wires 36 are utilized.

In the seventh embodiment thus configured, since the ignitor module isdivided into the power source circuit 7 d as the front end and the highvoltage generating circuit 7 e as the rear end, and also since the highvoltage generating circuit 7 c is further divided into the power sourceunit 71 a and the high voltage generating unit 72 a, the high voltagegenerating unit 72 a can be at least arranged within the lamp house 4Dor in proximity thereto (within the lamp house 4D in FIG. 12) with theremaining parts arranged in the other space. Thus, even if the lamphouse 4D affords no space for accommodating the entire ignitor module,the ignitor module can be successfully assembled with increasedreliability.

Also, the spark-gap (GAP) as well as capacitor C5 that determine thelife-time of the ignitor module can be replaced together with thedischarge lamp 13, the starting performance of the image displayapparatus can be refreshed each time upon replacement of the dischargelamp 13.

What is claimed is:
 1. An image display apparatus, comprising: acabinet, said cabinet accommodating therein: a discharge lamp; anignitor module which applies a high voltage to said discharge lamp forigniting the same; a lighting device which is connected to said ignitormodule and applies a discharging voltage to said discharge lamp so as tokeep said discharge lamp turned on; a signal processing unit providingan image signal in accordance with an input signal; an image displaywhich, in response to said image signal from said signal processingunit, produces an image to be projected by use of a light of saiddischarge lamp; and a power supply supplying electric power to saidignitor module, said lighting device, said signal processing unit, andsaid image display; wherein said power supply provides a voltage powerto said ignitor module through said lighting device, said ignitor moduleincluding a transformer which boosts said voltage power into a highvoltage, and including a high voltage generating circuit which appliesto said discharge lamp said high voltage, said lighting devicegenerating a voltage from said voltage power, after said discharge lampis ignited, for keeping said discharge lamp turned on; said ignitormodule being physically separated from said power supply as well as fromsaid lighting device, said cabinet accommodating said ignitor modulewithin a first interior space close to said discharge lamp, andaccommodating signal processing unit, said power supply and saidlighting device as being separated from said ignitor module within asecond interior space opposite from said first interior space, a lamphouse being provided to be detachable from said cabinet, said lamp househaving a lamp house interior space separated by a partition into twostorage spaces, one for receiving said discharge lamp, and the other forreceiving said high voltage generating circuit.
 2. The image displayapparatus as set forth in claim 1, wherein said ignitor module includesa lamp socket.
 3. The image display apparatus as set forth in claim 1,wherein said lighting device and said power supply are mounted on acommon board.
 4. The image display apparatus as set forth in claim 1,wherein said ignitor module and said lighting device are mounted on aflexible printed board.
 5. The image display apparatus as set forth inclaim 1, wherein said high voltage generating circuit is surrounded by acase having walls, at least one of said walls forming an outer wall ofsaid lamp house.
 6. The image display apparatus as set forth in claim 1,wherein said partition interrupts heat radiation from said dischargelamp to said high voltage generating circuit.
 7. The image displayapparatus as set forth in claim 1, wherein said lamp house accommodateslead wires for connection of said high voltage generating circuit tosaid power source circuit of said ignitor module, and for connection ofsaid discharge lamp to said lighting device, respectively, said lamphouse being provided with the partition which is disposed between saidlead wires and said discharge lamp.
 8. The image apparatus as set forthin claim 1, wherein said cabinet includes a fan which makes a forced-aircooling for the interior of said cabinet, said high voltage generatingcircuit being arranged upstream of said discharge lamp with respect to aforced-air flow of said fan.
 9. The image display apparatus as set forthin claim 1, wherein said storage section is filled with an insulationmaterial.
 10. The image display apparatus as set forth in claim 1,wherein said ignitor module is separated into a high voltage generatingunit for applying said high voltage to said discharge lamp, and a powersource unit which provides an electric power to said high voltagegenerating unit, said lamp house including a storage section whichreceives therein at least said high voltage generating unit.